The present invention generally relates to an amorphous magnetic wire and its method of production, and in particular to an amorphous magnetic wire which is applicable to magnetoelastic wave devices such as frequency filters, signal delay lines, position detecting sensors, non-volatile memories and the like, and the method of producing the above amorphous magnetic wire.
Conventionally, such magnetoelastic devices have been widely used in various fields. Magnetic substances used in magnetoelastic devices are required to have the following magnetic properties. The required magnetic properties are such that firstly magnetoelastic waves are easily generated in the magnetic substances, secondly magnetoelastic waves propagate through the magnetic substances with a low attenuation rate, and thirdly magnetoelastic waves in the magnetic substances are easily detected.
Recently, amorphous magnetic substances have become used. Amorphous magnetic substances satisfy the above requirements well, compared to other substances. Generally, amorphous magnetic substances are shaped like a thin film or thin ribbon. Presently, magnetic substances which are formed in a fine wire shape have been developed and recognized.
Mechanisms for the generation and detection of magnetoelastic waves in the amorphous magnetic substances are as follows. When magnetic field is applied to a portion of a magnetic substance by use of a coil for example, variations in magnetization following a magnetization curve are generated in the magnetic substance as variations in the applied magnetic field. The variations in magnetization cause magnetostriction, which is propagated through the magnetic substance as elastic waves. The elastic waves are magnetoelastic waves. Adversely, when there exist the magnetoelastic waves in the magnetic substance, the magnetostriction causes variations in magnetization due to an inverse magnetostrictive effect. The variations in magnetization changes a magnetic field around the magnetic substance. Therefore, it is possible to detect the variations in magnetization in the magnetic substance by use of a coil for example.
As described above, the magnetization properties and the magnetostriction play or the inverse magnetostriction an important role in the generation and detection of the magnetoelastic waves. That is, an decrease in the coercive force means that the magnetic substance becomes softer. The smaller coercive force generates the greater variations in magnetization in response to the smaller variations in the magnetic field. Therefore, the generation and detection of the magnetoelastic wave becomes easier. Alternatively, an increase in the coercive force means that the magnetic substance becomes harder. Therefore, the generation and detection of the magnetoelastic waves become more difficult. In addition, when the coercive forces are the same, the greater the magnetostriction, the easier are the generation and detection of the magnetoelastic waves. Both the relationship between the magnetic field and the magnetization, and the relationship between the magnetization and magnetostriction or inverse magnetostriction have an effect on a mutual function between the magnetic field and the magnetostriction, i.e., magnetoelastic coupling. As the magnetoelastic coupling becomes greater, the generation and detection may be made more easily.
On the other hand, when the magnetoelastic coupling is large, the magnetization varies with time due to the magnetoelastic waves propagated through the magnetic substance. The variations in the magnetization cause an eddy current, and thus increase a loss of propagation. The propagation loss increases as frequencies of the magnetoelastic waves increase.
As described above, the first and third requirements are opposite to the second requirement. That is, for magnetic substances having a large magnetoelastic coupling, the generation and detection of the magnetoelastic waves are relatively easy, but the propagation loss is large. On the other hand, for magnetic substances having a small magnetoelastic coupling, the magnetoelastic waves may be propagated through the magnetic substance with a low attenuation, but it becomes difficult to produce and detect the magnetoelastic waves.
Consequently, it is presently impossible to realize a magnetoelastic wave device capable of generating, propagating and detecting the magnetoelastic waves efficiently and effectively.
The conventional magnetoelastic substances has the following disadvantage. When trying to generate the magnetoelastic waves in the magnetic substance by a relatively simple device such as a coil or the like, the magnetic field of the driven coil is applied to the magnetic substance over a considerable length. Therefore, magnetoelastic waves which are excited at various portions within the range interfere each other, and are thus attenuated. Likewise, when trying to detect the variations in the magnetic field by a coil, the coil picks up the variations in the magnetization within the magnetic substance over its long length. This degrades an efficiency in detecting the magnetoelastic waves. It is noted that the above problems at the time of the generation and detection of the magnetoelastic waves become greater as frequencies of the magnetoelastic waves increase.
In order to solve the above problems, a combination of magnetic substances with different substances such as piezo materials has been proposed. The magnetic substance is used to propagate the magnetoelastic waves, and the piezo material is used to generate and detect the magnetoelastic waves. However, the structure of the magnetoelastic wave device is very complex and expensive.